This is a small bug that I found while doing the Rare Earth quest in Storm Peaks. I recently learned Mining anew and was still at 0 however noticed that my Mining went up for every "Rare Earth" that I dug up for this quest. These gains didn't stop until I reached 90 Mining. This may not be terribly useful if you are depending on Copper ore for your other tradeskill though is quite good if you just want to power your Mining up to 90 in no time at all.
Quick Guide for the reading-impaired:
1. Get the Rare Earth quest in Storm Peaks
2. Mine the Rare Earth
3. Get lots of gains
4. Delete Rare Earth so you can keep mining it until 90 Mining.